CASE OF THE MONTH - June 1996

Clinical Aspects

A 43-year-old woman was being investigated for dyspesia and had an ultrasound examination. This revealed an asymptomatic mass that appeared to involve the left kidney. Subsequent investigation established that the tumor was, in fact, intrarenal and a nephrectomy was performed. Post-operative clinical evaluation failed to disclose a neoplasm at any other site.

Pathology

Gross examination of the kidney showed a solid, homogeneous, tan tumor in the hilar region measuring 2.5 cm in maximum diameter. One pericaval lymph node contained metastatic tumor. The pathologist initially examining the gross specimen thought the appearance was somewhat unusual for renal cell carcinoma and a portion was fixed in glutaraldehyde for electron microscopy. By the time histological slides were available, ultrastructural evidence of many neurosecretory granules within tumor cell cytoplasm established the neoplasm as a primary or metastatic carcinoid (Figures 1 and 2). Also present was another feature common to carcinoids, intracytopasmic accumulations of intermediate filaments. In addition, typical features of renal cell carcinoma such as lumens with microvilli, lipid vacuoles and collections of glycogen were absent. Histology as complexly interconnecting cord of tumor cells was consistent with a carcinoid tumor (Figures 3 and 4).

To access electron micrographs, use Figure 1
To access light micrographs, use Figure 3.

Fig.1 Fig. 2 Fig.3 Fig. 4.

Diagnosis

Primary renal carcinoid

References

1. Acconia A, Miracco C, Mattei FM, deSanti MM, Del Vecchio MT, Luzi P: Primary carcinoid tumor of kidney: Light and electron microscopy, and immunohistochemical study. Uropathology 1988;31:517-520.
2. Huetter PC, Bird DJ, Chang YC, Seiler MW: Carcinoid tumor of the kidney with morphologic and immunohistochemical profile of a hindgut endocrine tumor: Report of a case. Ultrastruct Pathol 1991;15:655-661.
3. Stahl RE, Sidhu GS: Primary carcinoid of the kidney: Light and electron microscopic study. Cancer 1979;44:1345-1349.
4. Erlandson RA: Diagnostic Transmission Electron Microscopy of Tumors. New York; Raven Press, 1994. An example of a renal carcinoid is illustrated, on page 311, with identical features to the present case.
5. Raslan WF, Ro Jy, Ordonez NG, Amin MB, Troncoso P, Sella A, Ayala AG: Primary carcinoid of the kidney: Immunohistochemical and ultrastructural studies of five patients. Cancer 1993;72:2660-2666.
6. El-Naggar AK, Troncoso P, Ordonez NG: Primary renal carcinoid tumor with molecular abnormality characteristic of conventional renal cell neoplasms. Diagn Mol Pathol 1995;4:48-53.

Cases of the Month